MSC/Circ.860
22 May 1998
GUIDELINES
FOR THE APPROVAL OF OFFSHORE CONTAINERS HANDLED IN OPEN SEAS
1. The Maritime Safety Committee, at its
sixty-ninth session (11 to 20 May 1998), considered and approved draft revised
Guidelines for the approval of offshore containers handled in open seas, as set
out in the annex to this circular.
2. These Guidelines are based on the
provisions contained in the annex to MSC/Circ.613, which have been updated to
reflect more clearly the relevant provisions in the Recommendation on
Harmonized Interpretation and Implementation of the International Convention
for Safe Containers (CSC), 1972, as amended (CSC/Circ.100) and the IMDG Code
and recent practice in the design of offshore containers.
3. Member Governments are invited to bring
these Guidelines to the attention of all parties concerned with the approval,
manufacture, inspection and operation of offshore containers.
4. This Circular
replaces MSC/Circ.613 dated 18 June 1993.
ANNEX
GUIDELINES
FOR THE APPROVAL OF OFFSHORE CONTAINERS HANDLED IN OPEN SEAS
1 The Maritime Safety Committee, at its
sixty-second session, approved amendments to the Recommendation on Harmonized
Interpretation and Implementation of the International Convention for Safe
Containers, 1972 (CSC). The revised Recommendation was circulated as
CSC/Circ.100 dated 30 June 1993 and has been included as a supplement in the
1996 edition of the CSC.
2 Paragraph 3.3 of the revised
Recommendation on Harmonized Interpretation and Implementation of the CSC
states that the Convention does not apply to offshore containers that are
handled in open seas. There are several reasons for applying special design and
testing parameters to offshore containers:
.1 the tests set out in Annex II to the CSC
are designed to cover the forces on containers encountered in general marine
transport, loading and unloading in ports and in inland transport. However,
offshore containers are used to supply offshore installations and are typically
shipped on the open deck of purpose-built supply vessels and are lifted onto
and off the offshore installation by cranes on the installations. Such
operations may often take place in very unfavourable weather and sea
conditions;
.2 spreader beams, as used for lifting ordinary
containers, cannot be used when lifting offshore containers; and
.3 the types of offshore containers used are
often purpose-built and include closed and open dry cargo containers, dry bulk
cargo containers and portable tanks. Offshore containers, unlike ISO
containers, are not standardized with regard to sizes or gross mass; many have
a smaller base area than the 7 m2 in the lower limiting
definition of a container in the CSC.
3 Sections 12 and 13 of the General
Introduction to the International Maritime Dangerous Goods (IMDG) Code
recognize the special nature of offshore containers and portable tanks. These
sections state that the design and testing of offshore containers and offshore
tank-containers should take into account the dynamic lifting and impact forces
that may occur when a container or tank is handled in open seas in adverse
weather and sea conditions and that the requirements for such containers and
tanks should be determined by the approving competent authority.
4 For the purposes of these guidelines,
"offshore containers" should be taken to mean portable units
specially designed for repeated use in the transport of goods or equipment to,
from or between fixed and/or floating offshore installations and ships.
Such units include containers and portable tanks for dangerous goods as defined
in sections 12 and 13 of the General Introduction to the IMDG Code.
5 These guidelines are intended to
assist approving competent authorities in developing detailed requirements for
offshore containers. For the purposes of these guidelines, the "approving
competent authority" includes organizations duly authorized by the
Administration.
Approval
6 Approving competent authorities should
base their approval of offshore containers both on calculations and on testing,
taking into account the dynamic lifting and impact forces that may occur when
handling in open seas.
Design
7 Offshore containers should be fitted
with special pad eyes, suitable for the attachment of purpose-built slings
connected with shackles. Where ISO corner fittings are mounted in conjunction
with pad eyes, these corner fittings are not intended for lifting offshore.
8 In order to facilitate handling in
open seas, offshore containers should be pre-slung. Such slings should be
permanently attached to the container and considered to be part of the
container. The dynamic forces which occur when handling containers in open seas
will be higher than those encountered during normal quayside handling. This
should be taken into account when determining the requirements for slings on
offshore containers by multiplying the normal safety factor for slings by an
additional factor. The fact that light containers will be subject to relatively
higher dynamic forces than heavier containers should also be taken into
account. Minimum material requirements for impact toughness should be specified
when high strength steel is used in e.g. chains, links and shackles.
9 Since offshore containers may not
always be secured on supply vessels, such containers should be designed so as
to withstand 30o tilting in any direction when fully loaded. Cargo
may normally be assumed to be evenly distributed with the centre of gravity at
the half height of the container, but on containers for dedicated transport
(e.g. special bottle rack containers for gas bottles in fixed positions) the
actual centre of gravity should be used.
10 Protruding parts on an offshore
container that may catch on other containers or structures should be avoided.
Doors and hatches should be secured against opening during transport and
lifting. Hinges and locking devices should be protected against damage from
impact loads.
11 Strength calculations should include
lifting with the attached lifting sling and any other applicable means of
handling (e.g. lifting with fork lift trucks). Impact loads on the sides and
bottom of containers should also be considered in these calculations and impact
properties should be included in the requirements for structural steel
materials. However, calculations, including static equivalency of point loads
in combination with the tests as set out in paragraph 13 should normally be
considered sufficient.
12 Containers are sometimes temporarily
used on floating or fixed offshore installations as storage space,
laboratories, accommodation or control stations, etc. When used this way, the
container will also be subject to the regulations applicable for the offshore
installation in addition to transport related requirements based on these
guidelines.
Testing
13 At least one offshore container of each
design type should be subjected to the following tests:
.1 4-point
lifting test
Internal load: a uniformly
distributed load such that the total mass of the container and test load is
equal to 2.5R, where R is the maximum allowable combined mass of the container
and its cargo. The container should be lifted with a lifting sling attached to
each of its four pad eyes with an angle to the vertical equal to the design
angle.
.2 2-point
lifting test